> For the complete documentation index, see [llms.txt](https://maksimdan.gitbook.io/interview-practice-problems/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://maksimdan.gitbook.io/interview-practice-problems/leetcode_sessions/349_intersection_of_two_arrays.md).

# 349 Intersection of Two Arrays

Given two arrays, write a function to compute their intersection.

```
Example:
Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return [2].
```

Note:\
Each element in the result must be unique.\
The result can be in any order.

**The Idea:** The intersection of two arrays are the elements they have in common.

**Complexity:** O(N) time and space

```cpp
vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
    unordered_set<int> s(nums2.begin(), nums2.end());

    vector<int> intersect;

    for (auto i : nums1) {
        if (s.find(i) != s.end()) {
            s.erase(i);
            intersect.push_back(i);
        }
    }

    return intersect;
}
```

**Python**

```python
class Solution:
    def intersection(self, nums1, nums2):
        """
        :type nums1: List[int]
        :type nums2: List[int]
        :rtype: List[int]
        """
        if not nums1 or not nums2:
            return []
        return list(set(nums1) & set(nums2))
```


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://maksimdan.gitbook.io/interview-practice-problems/leetcode_sessions/349_intersection_of_two_arrays.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.